BS-2 Dividing Head - drive ratio from change-gear shaft?

[MRA]

hi folks

I am doing OK (I think!) in slowly getting my head around the maths of the relationship between bed travel, workpiece rotation, gear OD and desired helix angle when cutting helical gears.

These will be full-size gears. I know there are several very neat methods for making model ones, not least as suggested here - this video got me started thinking about this job for our museum again, when youtube's algorithm dropped it serendipitously into a list of suggestions of things for me to watch.



Find Hansen - goodness, what skill.

We will be using a Bridgeport (which I see has a 5tpi leadscrew) and a BS-2 dividing head. My problem is, I am away from the museum, and although I know that the main worm drive is 40:1, I have been unable to find out if there is a further reduction between the shaft one drives with change gears, and the shaft with which one usually rotates the chuck using the dividing plates / pin - or whether these two rotate at 1:1. If anyone happens to know this, it will give me time to work things out some more, before next time I am down there.

Thankyou -
Mark

 

[MRA]

Well, just in case it is of use to anyone else, I can confirm that a BS-2 dividing head has a 1:1 ratio between the shafts mentioned above - it is still 40:1 when driven from change gears. Or at least - that's true of ours!